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Published on May 15th, 2013 | by Scott Cooney


Refrigerator and freezer: ideal temperatures and humidities for efficient operation

empty refrigeratorBuying an energy efficient refrigerator is just one step toward cutting your utility bills and carbon emissions, and is not an option for many people either for cost or situation (i.e., they’re renting). In this post, we’re going to cover a “cool” (wow…a pun in the second line, sorry about that) way to check your refrigerator and freezer and make sure they’re operating at the most efficient level possible, while also treating your foodstuffs the way they should.

Two data points will help you set your fridge and freezer to their most efficient settings: temperature and humidity. A temperature that is set too cold will end up using too much electricity. A more humid fridge will require more energy to cool (simply because the water molecules in the air require cooling, too). So make sure things you store have a lid (will prevent moisture from escaping the food and into the fridge air…better for food, better for energy use).

So here’s what you do. Get yourself a hygrometer, a cool little gadget most commonly used for cigar storage, which measures both temperature and humidity.


Hygrometers come in a lot of shapes and sizes, and generally retail for about $20.

Using a hygrometer, test the temp and humidity in a variety of places in your fridge, especially the vegetable drawers. You ideally want an average temperature in your refrigerator of about 4-5 degrees C (37-40 degrees F), and a temperature of about -18 to -17 degrees C in your freezer (0-4 degrees F). You’ll notice, though, if you test a variety of locations in your fridge, you’ll learn where it’s coldest and where it’s warmest. From that, you can place more perishable and less perishable items accordingly.

In terms of humidity, many refrigerators come with drawers that have humidity settings. In general, you want stuff that will rot to be in the lower humidity drawers, and stuff that will wilt in higher humidity drawers.


Store in higher humidity

Store in lower humidity

Leafy greens




Green Onions







As a general rule, thinner stuff likely needs more humidity, thicker stuff less. Several readers on Green Living Ideas have pointed out that leafy greens and broccoli are actually best stored in just a bowl of water (think flowers), which will keep them really lively until you’re ready to eat them.

Putting a box of baking soda in your fridge will help dehumidify and deodorize it, making the fridge work less and also helping the fridge stay cleaner.

Other efficiency operation tips

Perhaps the most effective thing you can do no matter how new or old your fridge is, is to right-fill it. Think about what happens when you open the fridge door. Cold air comes rushing out. If your fridge is more full, less air comes out (that volume of air is replaced by a volume of something stored there). That reservoir of cold left in the fridge helps keep the fridge colder when it’s opened. Same thing goes for the freezer. So if you’re a bachelor with a chronically empty fridge, get some stuff you’ll never use (wine coolers?) and put them in your fridge. You can freeze containers of water, or get some extra bread, tofu, etc., to put in your freezer, to help prevent all the freezing air from escaping when you open it, as well.

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About the Author

Scott Cooney is a serial eco-entrepreneur including being the solo founder of Pono Home,, and CleanTechnica; author of two books; former sustainability consultant with clients including Johnson & Johnson, Eastman Chemical, Wal-Mart, and Duke Energy; former Adjunct teaching the first course in sustainable business in the MBA program at UH Manoa; lover of local, healthy food and especially vegan nachos. Find Scott on Twitter

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